The present invention relates to an airbag module and, more particularly, to an airbag module cover that includes an outer surface that forms part of a vehicle instrument panel.
In an airbag device for a vehicle, an airbag is typically accommodated in an airbag module that includes a retainer covered by a module cover. The retainer is connected to the vehicle structure, and the outer surface of the module cover faces into the vehicle passenger compartment. For a driver airbag device, the airbag module is mounted to a steering wheel of a vehicle. For a passenger airbag device, the airbag module is mounted to an instrument panel of the vehicle. In the event of a vehicle emergency such as a collision, an inflator in the airbag module delivers inflation gas into the airbag thereby inflating the airbag. As the airbag inflates, the airbag exerts pressure on the module cover. When sufficient pressure is exerted on the module cover, the cover ruptures and opens toward the inside of the vehicle cabin thereby allowing the airbag to be inflated inside the vehicle cabin to protect a vehicle occupant.
One disadvantage of conventional airbag modules is that the module cover must be made of materials that can be configured to rupture and that can withstand high airbag deployment temperatures. As a result, conventional module covers typically include an injection molded base layer having a pre-weakened portion such as a tear line groove that ruptures or breaks when sufficient pressure is exerted on the module cover by the inflating airbag. Conventional module covers generally also include a surface sheet disposed on the base layer so that the outer surface of the module cover matches the appearance and feel of the vehicle instrument panel. The surface sheet may include a lower layer formed of a thermally resistant resin, a middle layer formed of a soft foamed resin, and an outer decorative layer formed of a thermoplastic elastomer (TPE). The TPE can be, for example, polyolefin based (TPO), polystyrene based (TPS), polyvinyl chloride based, polyester based, polyamide based, or urethane based.
As a result of the above requirements and construction, the design and appearance (e.g., texture, color, pattern, surface finish) of conventional module covers is limited. Moreover, the thermoplastic elastomers forming the decorative layer are not well suited for application of coatings and paints thereby further limiting the appearance of the module cover so that desired customer finishes often can not be achieved.